Cold-starting and warm-up of internal combustion engines, particularly small engines in chainsaws, snowblowers, outboard marine engines and the like, have been and remain a problem in the art. In one system heretofore proposed, a solenoid valve is responsive to an operator manual key-switch or pushbutton prior to cranking or starting to feed fuel from a tank or supply to the air intake manifold to enrich the fuel/air mixture upstream of the engine carburetor. After the engine starts and begins to run, if the engine appears to be stalling, the operator must again activate the switch for a short period of time to re-enrich the fuel/air mixture and prevent stalling. Such operator-controlled enrichment systems require operator attention and intervention to enrich the fuel/air mixture for starting and to prevent stalling during warm-up. Further, there is the distinct possibility of over-enriching the fuel-air mixture and thereby flooding the engine.
Thus, there is a need for an automatic engine enrichment system for use with internal combustion engines of the described character that does not require operator intervention, and thus is independent of training and attention of the operator, that is automatically responsive to engine operation for selectively enriching the fuel/air mixture during both cranking and warm-up, that is economical to implement, that is reliable over an extended operating lifetime, and that requires minimum adaptation to particular engine designs and requirements. It is an object of the present invention to provide an automatic engine fuel enrichment system of the described character that satisfies some or all of the aforementioned deficiencies in the art.
Another object of the present invention is to provide system for controlling engine advance angle so as to assist engine operation and prevent stalling during both warm-up and normal operation.